Max power (with akceptable efficiency) of the motor is about
Pin[W]=1600*Vmagnet[inch^3]
Pin[W]=0.1*Vmagnet[mm^3]
This formula is based on practice, and work well on neodym magnet. It is very usefull to calculate an appropriate max. supply voltage, rpm, proppeler etc. (based on the motor resistance and expecting efficiency or simply optimal motor current)

How does one calculate how many magnets to use against the number of poles, and what decides the winding direction? Anyone please?
Thanks Brian

Excellent motor building articles by Brian Mulder, a must read, will prevent you from asking a lot of questions you even did not know you were going to ask http://www.southernsoaringclub.org.za/
-> Articles by SouthEasterners.
-> Electric Motors - part 1-5
-> Table in chapter 3

Do-it-yourself motor homepages, manuals/tutorials, checks and tests in this motor builders tips and tricks thread. The checks and tests may save you from frying your controller or motor. Thread is active, bookmark it for future reference and subscribe to it:https://www.rcgroups.com/forums/showthread.php?t=240993 (sticky thread, at top of subforum)

I've seen a few posts that you have made on forums regarding motors and you seem to know your stuff. I've only been in the RC arena for about 4 months now but this is my background. I learned to fly planes on a Stryker F-27C, went to Hanger 9 F-22 Raptor (Nitro, which I do not like now, prefer electric) and from that point I've been flying FunJets (3 with Mega 16/15/3 (3000kv) & Align 430XL (3770kv), Kyosho F-16 EDF and Phase 3 F-16 EDF. Here's my question. I've been told by a couple people that I could actually make my own motors which is why I am here, researching. You seem to be one of the guys to talk to. This is what I am trying to attempt. I want to take the last 3 planes mentioned and make them scream and would like your advise on how to make motors that will make these birds scream. I know its not as simple as that, but I was hoping you could point me in the right direction towards winding my own motors to suit my needs. Currently for the Phase 3 F-16 the fastest flyers seem to be running Typhoon 2W & 2W-20/23's with Wemo mini fans or Alfa 5 blade fans. Others motors are Little Screamer Jet Screamers and a new Monster Jet Screamer that hasn't been released yet. I was talking to the R&D guy who is putting it into a WM400 fan unit and they're talking about doing about 160 - 170 mph with that set up. Can I make motors that will help me reach at least 120 mph or more by either prop or fan unit? I would sincerely appreciate any information you might pass my way. Thank you in advance and I look forward to hearing from you and others in the forum.

Do-it-yourself motor homepages, manuals/tutorials, checks and tests in this motor builders tips and tricks thread. The checks and tests may save you from frying your controller or motor. Thread is active, bookmark it for future reference and subscribe to it:https://www.rcgroups.com/forums/showthread.php?t=240993 (sticky thread, at top of subforum)

Do-it-yourself motor homepages, manuals/tutorials, checks and tests in this motor builders tips and tricks thread. The checks and tests may save you from frying your controller or motor. Thread is active, bookmark it for future reference and subscribe to it:https://www.rcgroups.com/forums/showthread.php?t=240993 (sticky thread, at top of subforum)

Motors are not resistors, they behave differently. You have to halve the number of winds. That will gave you the same rpm. No you have room for thicker wire, that's nice because motorcurrent has doubled.

Ok , thanks ........ the wire will give me a very low resistance but i must not "think to much" about the resistance .

I must "think only" about KV ( halve the number of turns and give the stator the "maximum of copper" , maximum thickness to the wire ) , and "to say to me" that the maximum thicker wire does not want to say bad efficiency for the motor .